1. Field of the Invention
The present invention relates to a heating apparatus for heating a gas, a liquid, a solid and the like.
2. Description of the Related Art
Conventionally, heating systems for heating by gas, such as instantaneous water heaters, have been used in order to rapidly raise the temperature of a liquid. In order to heat a solid, metal sheathed tubular elements have been used, for example.
When water is rapidly heated by a conventional instantaneous water heater, the temperature of a heat transfer surface to water exceeds a boiling point due to an excessive calory density. Thus, local boiling is easy to generate, which results in poor safety.
In order to avoid local boiling, a heat exchange area needs to be increased, but an increased heat exchange area enlarges the heating apparatus because of the structure of the combustion section.
Moreover, heating by gas, which is performed from outside a pipe through which water flows, has a low thermal efficiency.
In the case of an electric water heater, a local abnormal temperature rise is easily generated due to an excessive electricity density. This type of water heater also has problems of a low level of safety at the time of and disconnection of the heater. Accordingly, the electric water heater is not suitable to boil water to a temperature close to a boiling point.
In the case where a solid having poor thermal transfer is heated by metal sheathed tubular elements, the temperature is excessively raised only in a portion opposed to the metal sheathed tubular elements, which acts as a heat source.
In the case where the heat exchange surface is increased in order to avoid generation of local heating, the heating apparatus is enlarged and also the heat capacity of the heater is increased. Thus, the temperature response is deteriorated.
In a heating apparatus for heating and thus recovering an adsorbent such as active carbon or zeolite, it is necessary to increase the heat exchange area so as to increase the surface to contact the adsorbent. When a conventional electric heater is used, the heating apparatus is enlarged and the recovering efficiency is low due to the non-uniform temperature of the electric heater.
In a conventional heating apparatus for heating water to generator vapor, the rise is slow and the energy efficiency is low since the water in the reservoir is heated. In a structure in which vapor is instantaneously generated, the heat exchange area needs to be increased, and thus the heating apparatus is enlarged.
When a conventional electric heater is used in a heating apparatus for purifying the air using a catalyst, the effective reaction area cannot be increased due to a limit in the thermal transfer in the carrier (catalyst). Accordingly, the purifying capability is low.
Furthermore, a conventional heating apparatus requires a thermostat and a temperature fuse to be installed in the vicinity of the heat source, resulting in a complicated structure of the heating apparatus.
A conventional electric water heater further has the problem in that scale is accumulated on the surface of the heater and thus abnormal heating disconnects a part of the electric heater to which the scale adheres.